Green ceramic insert, ceramic insert, ceramic green body or green body composite and ceramic laminated composite produced thereby

ABSTRACT

A green ceramic insert having a green ceramic body provided with a recess extending through the ceramic body is provided, the recess being filled with a paste which may be converted into an electrical plated hole. A ceramic insert made from a sintered green ceramic insert of this type is also described. In addition, a ceramic green body or a green body composite is provided, which has at least one recess in some areas, into which one of the described green ceramic inserts is inserted. The ceramic insert may be integrally joined to the laminated composite, a conductive paste converted by sintering into a printed conductor being routed on the laminated composite in a manner electrically insulated from it, and electroconductively connecting the top of the laminated composite to its bottom via the electrical plated hole.

FIELD OF THE INVENTION

The present invention relates to ceramic inserts, bodies and composites.

BACKGROUND INFORMATION

In the manufacture of planar exhaust gas analyzer probes, such ascustomary lambda sensors based on thick-film technology, electricallyinsulated plated holes known as vias are used to connect, for example,printed conductors on different sensor levels or the front or back of aceramic laminated composite.

If the material from which the ceramic green films are made iselectrically insulating, e.g., an LTCC ceramic based on Al₂O₃ (where“LTCC” denotes a low-temperature co-fired ceramic), a hole is drilled orpunched into the ceramic green film and filled with a paste filled witha conductive material such as silver or platinum, as is customary in themanufacture of printed conductors.

It is more difficult to produce an insulated plated hole, which issuitable for electrically poorly conductive film materials such asyttrium-stabilized zirconium dioxide.

In order to be able to implement an electrical plated hole in the caseof ceramic green films containing yttrium-stabilized zirconium dioxide,from which an yttrium-stabilized zirconium dioxide ceramic is producedafter sintering, the use of a platinum-containing paste, to whichniobium oxide (Nb₂O₅) is added, has been described. The latter is ableto compensate the yttrium oxide doping of the zirconium dioxide,resulting in a stoichiometry of the ion conductor “yttrium-stabilizedzirconium dioxide” in the area of the via or the electrical plated hole,which is characterized by a relatively low electrical conductivity.

An additional technique for integrating electrically insulated platedholes in conductive, ceramic multilayered structures is to introduce ahole for the electrical plated hole into the green film(s), and then tocoat or to wet this hole on the wall of the green film(s) delimiting thehole with an insulation paste and then to introduce the conductivematerial, i.e., the platinum-filled paste, for example, into the nowinsulated hole.

A disadvantage of the above-described method for producing the platedhole and of the previously produced plated holes is that at hightemperatures, the Nb₂O₅ counter-doping is made partially ineffective sothat the insulation resistance to the electrical plated hole issignificantly reduced. Furthermore, the suction of two different pastes,first an insulation paste and then a conductive paste is very difficult,in particular in a multilayered composite of ceramic green films or aceramic laminated composite (manufactured from it by sintering) becauseit is hardly possible to ensure that the insulation layer applied firstto the inner walls is entirely free from cracks and thus reliablyprevents the conductive paste from contacting the electricallyconductive ceramic green films and the ceramic layers sintered from it.

Moreover, the insulating effect of known insulated plated holes isgenerally low at high temperatures in particular because insulatinglayers used previously have only low layer thicknesses due to theirmethod of manufacture.

As a whole, it has thus far not been possible to ensure a reliable,high-resistivity insulation of a via using a ceramic laminated compositeor a ceramic layer at high temperatures of use.

SUMMARY OF THE INVENTION

In contrast to the related art, the green ceramic insert of the presentinvention, the ceramic insert sintered from it, the ceramic green bodyor ceramic green body composite of the present invention having a greenceramic insert of this type and the ceramic laminated compositemanufactured from it by sintering have the advantage that it is possibleto use them to achieve a very reliable, safe and high-quality electricalinsulation in the area of an electrical plated hole or via in ceramiclayers or ceramic laminated composites even for high-temperatureapplications and in the event of a plurality of plated hole planes.

It is advantageous in particular if the green ceramic insert has aprismatic, rectangular or cylindrically shaped ceramic body having around or ellipsoid cross-section when viewed from the top, a recessbeing placed in it concentrically, traversing it in particular, which isfilled with a customary paste which is convertible into the electricalplated hole by sintering, for example.

In order to ensure optimum electrical insulation of the electricalplated hole in relation to the adjacent areas of the ceramic green bodyor laminated composite, which is at least in some areas made ofyttrium-stabilized zirconium dioxide, for example, it is advantageous ifthe green ceramic body is convertible by sintering, for example, into anelectrically or poorly conductive or non-conductive ceramic, forexample, a ceramic made essentially from Al₂O₃, in relation to theelectrical plated hole and also to the ceramic laminated compositepresent in its surroundings after sintering.

The paste filled into the green ceramic insert in the area of the recessmay be filled with an electrically conductive material such as platinumor aluminum. This paste may be filled into the recess in the greenceramic body in such a way that at least on one side, or both sides, itprojects from the green ceramic body or surmounts it in the area of theoutlet orifices of the recess, so that, in a subsequent method step, itis possible to connect these projecting paste areas with a conductivepaste, pressed on the top and/or the bottom and structured in particularas printed conductors, in a particularly simple and reliable manner.

The dimensions of the recess in the ceramic body may be 50 mm to 2 mm indiameter at a diameter of the green ceramic body of between 0.5 mm to 5mm.

It is further very advantageous in particular if the ceramic green bodyor the composite of ceramic green bodies, into which the green ceramicinsert is or will be inserted, has a recess, which is dimensioned tomatch as exactly as possible the shape of the green ceramic insert or isslightly larger, and which simultaneously connects the top of the greenbody or green body composite with the bottom of the green body or greenbody composite. In this connection, it is further advantageous if thematerial of the green ceramic insert is matched to the material of thesurrounding ceramic green body or green body composite in such a waythat after insertion, the material of the green ceramic insert expandssomewhat within the recess during sintering and is thus secured in therecess, i.e., solidly anchored there. In particular, this ensures thatthe green ceramic insert is integrally joined to the surrounding greenbody or ceramic green body composite, the conductive paste converted bythe sintering into a printed conductor or structured conducting surfacesimultaneously electrically conductively connecting the top of theceramic laminated composite to its bottom.

The slight expansion of the material of the green ceramic insertproduces both a solid, precisely fitting seat in the recess in theceramic green body or ceramic green body composite and also brings abouta certain manufacturing tolerance.

In order to improve the bond or the seat of the inserted green ceramicinsert in the ceramic green body or green body composite in the area ofthe recess introduced in it, it is further advantageous if the inside ofthe recess in the ceramic green body or green body composite isadditionally coated at least in some areas with a binder paste or aslurry, such as a customary film binder paste before the green ceramicinsert is inserted.

In order to be able to route printed conductors or structured conductingsurfaces produced on or also in the ceramic green body or green bodycomposite or the ceramic laminated composite produced from it aftersintering from it to the produced electrical plated hole so that theyare electrically insulated, it is advantageous if the top and bottom ofthe ceramic green body or green body composite or at least individualceramic green films constituting it are provided on at least one side,on both sides in particular, and at least in some areas with anadditional green ceramic insulating layer, which after sintering isconverted into ceramic insulating layers based, for example, on Al₂O₃.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a through 1 d show cross-sectional views corresponding todifferent method steps for manufacturing a ceramic green body having aninserted green ceramic insert according to an embodiment of the presentinvention.

FIG. 2 shows an alternative exemplary embodiment of the ceramic greenbody.

DETAILED DESCRIPTION

In a first exemplary embodiment explained with reference to FIGS. 1 athrough 1 d, an electrical plated hole is at first produced as an inlayseparate from a ceramic green film, which is convertible by sintering,for example, into a highly insulating material such as Al₂O₃, a recesslocated within this inlay being filled with a paste before sintering,the recess being converted by sintering into the electrical plated hole.The inlay is then inserted in the form of a plug into a, for example,predrilled or prepunched hole in a ceramic green film or even in a greenfilm composite, after which printed conductors are then further printedonto the top or the bottom of the ceramic green film before the overallstructure thus produced is then finally sintered into a ceramiclaminated composite.

FIG. 1 a shows a ceramic green film 10 based on yttrium-stabilizedzirconium dioxide, both sides of which are provided with a thin greenceramic insulating layer or insulating film 12, which is convertible bysintering into an Al₂O₃ ceramic. In addition, a recess 11 in the form ofa cylindrical hole has been introduced in ceramic green film 10. Recess11 may be introduced into green film 10 both after the application ofinsulating layers 12 onto green film 10 as well as before theirapplication.

FIG. 1 b shows the interior walls 13 of green film 10 are coated with afilm binder paste 13′ in the area of recess 11 in a subsequent methodstep.

FIG. 1 c shows how a green ceramic insert 20 is produced concurrent withor before or after method steps 1 a or 1 b, the size of it being matchedto the size of recess 11 or having a slightly smaller diameter.Corresponding to recess 11, green ceramic insert 20 is cylindrical andhas a continuous recess 15 in the form of a hole having a circularcross-section, which is surrounded by a similarly cylindrical greenceramic body 14.

Green ceramic body 14 is, for example, punched out from a ceramic greenfilm, which is convertible by sintering into an electrically highlyinsulating ceramic, an Al₂O₃ ceramic, for example.

Subsequently, recess 15 traversing green ceramic body 14 is filled witha paste 15′, which contains an electrically conductive material such asplatinum or aluminum and is convertible by sintering into an electricalplated hole.

According to FIG. 1 c, paste 15′ slightly surmounts ceramic body 14 onboth sides.

FIG. 1 d shows the further method steps, green ceramic insert 20according to FIG. 1 c having been inserted into recess 11 according toFIG. 1 b, and subsequently a conductive paste 16, which is known, in theform of printed conductors or conductive layers having been pressed insome areas onto the top or the bottom of ceramic green body 5 thusproduced. Conductive paste 16 may be identical to paste 15′, which formsthe electrical plated hole.

Thus on the whole, a ceramic green body 5 is produced according to FIG.1 d, the top being connected to the bottom via an electrical platedhole, which is present in the area of recess 15, this electrical platedhole simultaneously being electrically insulated in relation to greenfilm 10 by green ceramic body 14. Furthermore, conductive paste 16 isinsulated in relation to green film 10 by insulation layers 12.

Finally, ceramic green body 5 according to FIG. 1 d is sintered,resulting in a ceramic laminated composite.

Moreover, it may be noted that due to the dimensions and the flexibilityof ceramic green films 10, 12 used, they normally have adequatestability for the provided method steps so that, for example, greenceramic insert 20 is inserted into recess 11 without any particulardifficulty with respect to process engineering.

FIG. 2 shows a second exemplary embodiment in which a composite ofceramic green bodies or a green film stack 5′ is shown, which is made upof a plurality of individual ceramic green films 10, each havinginsulation layers 12 according to FIG. 1 b applied to both surfaces ofthe green film.

In this case also, a green ceramic insert 20 according to FIG. 1 c isinserted into ceramic green body composite 5′, the green ceramic insertnow corresponding to the height of the ceramic green body composite 5′or is sized corresponding to recess 11 according to FIG. 1 b.

On the whole, after final sintering of composite of ceramic green films5′ according to FIG. 2, an electrical plated hole is obtained in aceramic laminated composite, which presses through a plurality of filmlayers simultaneously. Moreover, pressed-on, structured conductive paste16 according to FIG. 1 d, which is present there, is not shown in FIG. 2for reasons of clarity.

1. A green ceramic insert, comprising: a green ceramic body including arecess, the recess traversing the green ceramic body and filled with apaste that is convertible into an electrical plating, wherein the greenceramic body includes at least one of: aluminum oxide, and a materialthat is substantially convertible into a ceramic aluminum oxide body bysintering.
 2. The green ceramic insert of claim 1, wherein the greenceramic body is converted into a ceramic by sintering, the ceramic beingone of electrically non-conductive and poorly conductive in relation tothe electrical plating.
 3. The green ceramic insert of claim 1, whereinthe ceramic body is cylindrical and has one of a round and ellipsoidcross section when viewed from the top and the recess is centered in theceramic body.
 4. The green ceramic insert of claim 1, wherein the recessis cylindrical and has one of a round and ellipsoid cross section whenviewed from the top.
 5. The green ceramic insert of claim 4, wherein therecess is stamped out from the green ceramic body.
 6. The green ceramicinsert of claim 1, wherein the paste includes an electrically conductivematerial and is inserted into the recess of the ceramic body such thatthe paste extends beyond at least one surface of the ceramic body. 7.The green ceramic insert of claim 6, wherein paste includes at least oneof platinum and aluminum, the recess includes an outlet orifice at eachend, and the paste extends beyond at least one of the outlet orifices ofthe recess.
 8. The green ceramic insert of claim 1, wherein the recesshas a diameter between approximately 50 μm to 2 mm.
 9. The green ceramicinsert of claim 1, wherein the green ceramic body has a diameter betweenapproximately 0.5 mm to 5 mm.
 10. A ceramic insert, comprising: asintered green ceramic body including a recess, the recess traversingthe green ceramic body and filled with a paste that is convertible intoan electrical plating, wherein the green ceramic body includes at leastone of aluminum oxide and a material that is substantially convertibleinto a ceramic aluminum oxide body by sintering.
 11. A ceramic greenbody, comprising: a body section; and at least one recess situatedwithin the body section, the at least one recess including a greenceramic insert having a further recess, the further recess traversingthe green ceramic insert and filled with a paste that is convertibleinto an electrical plating, wherein the body section of the ceramicgreen body includes yttrium-stabilized zirconium dioxide.
 12. Theceramic green body of claim 11, wherein the at least one recess is oneof configured to match the shape of the green ceramic insert andslightly larger than the green ceramic insert, and extends from a top ofthe ceramic green body to a bottom of the ceramic green body.
 13. Theceramic green body of claim 11, further comprising: one of a binderpaste and a slurry at least partially coating an interior surface of theat least one recess within the body section.
 14. The ceramic green bodyof claim 13, wherein the interior surface is completely coated with oneof the binder paste and the slurry.
 15. The ceramic green body of claim11, wherein the body section includes a green ceramic insulating layeron at least one side.
 16. The ceramic green body of claim 15, whereinthe body section is completely covered on top and bottom sides with thegreen ceramic insulating layer.
 17. The ceramic green body of claim 16,wherein a conductive paste configured as a flat printed conductor issituated on a section of at least one of a top and a bottom surface ofthe ceramic green body, the conductive paste being in contact with thepaste filled into the further recess of ceramic green body.
 18. Theceramic green body of claim 17, wherein the conductive paste isseparated from the ceramic green body by the green ceramic insulatinglayer.